Impact of Air Pollution Control Devices on Selenium in FGD and Wastewater Treatment Systems at Coal-Fired Boilers

摘要

Selenium can be toxic to aquatic life in high concentrations, even though it is an essential nutrient at lower concentrations. Processing fossil fuels (e.g., petroleum refining, coal combustion) can result in release of selenium to water bodies. Although there is currently no federal limit on selenium discharge from coal-fired wet FGD systems, some plants in the U.S. have limits on discharge of selenium from flue gas desulfurization (FGD) systems based on state water permits. Gaseous selenium post-combustion can be removed by wet FGDs as well as other air pollution control devices (APCDs). Removal of selenium before the FGD reduces the potential discharge of selenium in the wastewater. In this study, the behavior of selenium in limestone forced oxidation FGDs is modeled to determine how the concentration of selenium in FGD liquor depends on upstream APCDs such as ESP, fabric filter, and dry sorbent injection (DSI) as well as the operation of the FGD itself.